In case you are interested, I leveled up my Stegodeus from level 26 to level 27. Since all the components were at 0 DNA I was able to track exactly what it took.
Apatosaurus DNA = 23,600
Nodosaurus DNA = 5,900
Stegosaurus DNA = 27,500
Coins for fusing = 22,800
Coins for the level up = 120,000
Experience Points for fusing = 96,300
Experience Points for leveling = 37,500
Average DNA per fuse was about 23. Yes I know that Stegodeus will likely be nerfed for 1.4. But it will still be the best on my team.